Caption: Shepherd's purse seed. Light micrograph of a longitudinal section through a seed of the shepherd's purse (Capsell bursa-pastoris), showing the embryo in the seed. The seed coat (testa) is a single layer of thick-walled cells covered with a thick cuticle. The embryo (bottom) has a large basal cell (white), a basal radical (above the white basal cell), then a short stalk (hypocotyl), then the top of the shoot (plumule, very small). Most of the seed consists of the large lamella-like cotyledons (pink), the first seed leaves. Magnification: x45 when printed at 10 centimetres high.